High output power high frequency resonant load inverters

• US 6,842,355 B2
• Filed: 09/28/2001
• Issued: 01/11/2005
• Est. Priority Date: 09/29/2000
• Status: Expired due to Term

• Current Assignee: EFD Induction Incorporated
• Original Assignee: EFD Induction Incorporated
• Inventors: Kleveland, Frode
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US10/381,415
• Publication Number:
  US 20030179595A1
• Time in Patent Office: 1,201 Days
• Field of Search: 363/95, 363/97, 363/98, 363/131, 363/132, 219660-665
• US Class Current: 363/132
• CPC Class Codes: H02M 1/0043 Converters switched with a phase shift, i.e. interleaved non-isolated DC/DC converters H02M3/1586
• CPC Class Codes: H02M 7/4815 Resonant converters H02M7/4811 and H02M7/4826 take precedence
• CPC Class Codes: H02M 7/493 the static converters being arranged for operation in parallel
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A new control strategy for IGBTs when used in high frequency (75 kHz-500 kHz) high power (10 kW-5 MW) inverters with series resonant load, a topology commonly used for induction heating. The strategy changes the IGBT strain elements into a total stress picture that fits the IGBP'"'"'s behaviour and internal nature better. This makes the IGBT operate much more efficient, thus increasing the maximum output power from the inverter significantly compared to a standard control scheme. This makes the IGBT based inverter a much cheaper alternative than a MOSFET inverter, which has been state of the art for this application.

Claims

1. High power, high frequency resonant load inverter system for providing increased output power, the system comprising:

an inverter device which is subdivided into parallel sections, each section comprising two sets of current switches, each set having two IGBT (Insulated Gate Bipolar Transistor) switch means connected in series, each set having an output at a midpoint between said means for feeding a respective input terminal on a power load having an LC resonant compensation, and a main driver circuit for controlling each IGBT switch means of each set, said inverter device operating with a reduced switching frequency which is lower than a LC resonant frequency by providing driver signals from said main driver unit to one section at a time, thus causing the switching frequency of each section to become 1/n of said resonant frequency, n being the number of sections.

2. The system according to claim 1, wherein a power transformer is connected between said outputs and said input terminals.

3. The system as claimed in claim 1, wherein said LC resonant compensation is an LC series resonant compensation, and wherein said sections have a DC voltage power supply.

4. The system as claimed in claim 1, wherein said LC resonant compensation is an LC parallel resonant compensation, and wherein said sections have a DC current power supply.

5. The system according to claim 3, wherein the system delivers a continuous sinusoid output current and a continuous rectangular output voltage.

6. The system according to claim 4, wherein the system delivers a continuous rectangular output current and a continuous sinuoid output voltage.

7. The system according to claim 5, wherein said output current and said output voltage are at least substantially in-phase.

8. The system according to claim 1, wherein the inverter device provides an operation frequency in the range of 75 kHz-500 kHz.

9. The system according to claim 1, wherein the inverter device provides an output power in the range of 10 kW-5 MW.

10. The system according to claim 1, wherein the system is used for operating an inductive load in an induction heating or contact welding operation device.

11. The system as claimed in claim 2, wherein said LC resonant compensation is an LC series resonant compensation, and wherein said sections have a DC voltage power supply.

12. The system as claimed in claim 2, wherein said LC resonant compensation is an LC parallel resonant compensation, and wherein said sections have a DC current power supply.

13. The system according to claim 6, wherein said output current and said output voltage are at least substantially in-phase.